Pump

ABSTRACT

A fluid pump of the type in which a housing assembly has a first sub-housing having an electric motor therein which is in line with a second sub-housing having the impeller therein, with the motor having a rotor shaft which extends through a seal of the first sub-housing into the second sub-housing and with the impeller mounted on the rotor shaft so as to be rotatable by the motor, and the second sub-housing having inlet and outlet ports through which fluid, such as water, is able to be pumped through the second sub-housing.

BACKGROUND ART

The improvements of the present application relate principally, but notexclusively, to fluid pumps of a type in which a housing assembly has afirst sub-housing having an electric motor therein which is in line witha second sub-housing having an impeller therein, with the motor having arotor shaft which extends through a seal of the first sub-housing intothe second sub-housing and with the impeller mounted on the rotor shaftso as to be rotatable by the motor. The second sub-housing has inlet andoutlet ports through which fluid, such as water, is able to be pumpedthrough the second sub-housing.

Fluid pumps of the type described are suitable for pumping water to thejets of a spa-bath or spa-pool installation, or for meeting therequirements for water pumping for a swimming pool. The presentimprovements are suitable for such applications, although they also canbe used in other suitable installations.

DISCLOSURE OF THE INVENTION

In a first aspect of the present application, there is provided animpeller suitable for use in a fluid pump of the type described,although the impeller is able to be used in other forms of pump. Theimpeller has a first and a second annular plate which are axially spacedand, located between the plates, an angularly spaced array of vanes. Theimpeller also includes a central hub which is within and radially spacedfrom the inner periphery of the first annular plate, and by which theimpeller is mountable on a shaft for rotation therewith. A plurality ofcircumferentially spaced connectors, extending between the first annularplate and an outer peripheral surface of the hub, secure the hub inrelation to the first plate, while an annular array of openings betweenthe inner edge of the first plate and the hub and between successiveconnectors enable fluid to be pumped to be drawn therethrough and intothe space between the plates.

The impeller may be made of any suitable moldable or castable material,such as a metal or a plastics material. The impeller may be of integralform, although it may achieve that form by at least two separatelyformed component parts being welded or bonded together. In one suitablearrangement, the impeller is made of a suitable plastics material, withcomponent parts being made integral by ultrasonic welding.

The first plate and the hub may be integrally formed, with the secondplate made separately. The vanes provided between the plates may beformed integrally with either plate. However, in a preferred form of theimpeller, the second plate preferably is flat with the first plate beingof shallow frusto-conical form such that the spacing between the platesdecreases towards the outer periphery of the impeller. Particularly withthat form, the vanes preferably are formed integrally with the firstplate, with the second plate then being welded or bonded to an edge ofeach vane remote from the first plate.

The impeller need not be of integral form. In one suitable form, it ismade of at least two separately formed component parts which are securedtogether by a suitable engagement therebetween. In one suitable form,the impeller is made of a suitable stiff material which has sufficientresilience to enable component parts to be secured together by a firmsnap-fit therebetween. Thus, for example, the second plate may have aplurality of axially extending fingers which extend away from its innerperiphery and which, with the second plate presented axially to thefirst plate, engage behind a shoulder or ledge defined by the hub andthereby secure the first and second plates in opposed relationship.

The vanes located between the plates may be arcuate so as to extendoutwardly in a spiral array. These vanes are operable to enhancecentrifugal force imparting velocity to a fluid being pumped outwardlybetween the outer periphery of the plates.

The connectors may extend substantially radially between the innerperiphery of the first plate and the outer surface of the hub. Eachconnector may be in the form of an inlet vane, although the array ofinlet vanes preferably has a neutral effect on fluid being pumpedthrough the openings towards the second plate. Within the spacingbetween the plates, fluid moves axially and then radially outwardly by apressure differential between the eye of the impeller at the connectorsand the outer periphery of the plates.

The hub may have a central boss by which the impeller is mountable on ashaft. Radially outwardly from the boss, the hub may have a peripheralskirt which defines the outer surface at which the hub is secured inrelation to the first plate by the connectors. The skirt preferablyflares from an end of the boss located beyond the first plate, in anaxial direction away from the second plate. At that end of the boss, thehub may have a convex, preferably part-spherical, surface which assistsin guiding fluid in its flow through the eye of the impeller.

The hub, at the other end of the boss, may terminate intermediate thefirst and second plate. In such case, the skirt of the hub may extend ashort distance beyond the other end of the boss, to enable a sealprovided on the shaft to be received in, and provide a seal around aninner peripheral surface of, the skirt. The boss has a bore extendingaxially from its other end, for receiving the shaft, and the bore may bea blind bore.

Around the inner periphery of the first plate, there may be an annularskirt which extends axially away from the second plate. The skirtdefines an inlet guide for fluid being drawn through the eye of theimpeller. The inner surface of the skirt preferably is opposed to partof the outer peripheral surface of the hub.

For some applications, the second plate may have an inner periphery atwhich, with the impeller mounted on a shaft, a fluid seal is provided bya seal provided on the shaft. However, for a principal application, theimpeller is intended to be mountable on a shaft with the inner peripheryof the second plate defining an annular clearance around the shaft andany seal on the shaft adjacent to the second plate. As a consequence,fluid is able to flow into the space between the plates, axially of theimpeller, from a surface of the second plate which is remote from thefirst plate. The reason for this will become clear from subsequentdescription herein.

Particularly where the inner periphery of the second plate is to definesuch a clearance around the shaft, there may be an annular spigot or finwhich projects axially from the remote surface of the second plate, awayfrom the first plate. The spigot or fin is disposed concentrically withrespect to the inner periphery of the second plate, but preferably isspaced outwardly therefrom but inwardly with respect to the outerperiphery of the second plate. The purpose of this spigot or fin alsowill become clear from subsequent description herein.

In a second aspect of the present application, there is provided a fluidpump of the type described, wherein the first sub-housing containing themotor is of double-walled construction enabling fluid cooling of themotor. The double-walled construction is provided by a motor casingwhich houses the stator and rotor shaft of the motor and, spaced fromand enclosing the motor casing, an outer shell. Within a chamber of thefirst sub-housing defined between the casing and shell, there isprovided a plurality of elongate baffles for guiding cooling fluid forflow over a major part of the external surface of the casing whereby theoperating temperature of the motor is able to be controlled by heatenergy extracted by the fluid from the casing.

The baffles may be of a form providing for a flow of cooling fluid alongsubstantially the full axial length of the motor casing. The flowpreferably is from a first end of the first sub-housing adjacent to thesecond sub-housing, along the casing to its second end and then backalong the casing to the first end. To enable this flow, there arealternating longer and shorter baffles, with the longer bafflesextending at least to the second end of the casing and the shorterbaffles terminating short of the longer baffles at that second end.Thus, cooling fluid is able to flow to the second end of the casingbetween alternate pairs of baffles, and then pass around the end of eachshorter baffles of each pair for return flow to the first end of thecasing between next adjacent pairs of baffles.

The chamber of the first sub-housing, defined between the casing and theshell may extend radially inwardly of the casing, towards the rotorshaft, at the first end of the first sub-housing. The baffles may havelateral portions, which extend across that end of the casing from theirmain longitudinal extent, such as to a central boss through which theshaft extends. Thus, the cooling fluid is able to extract that energyfrom the casing at the first end, as well as from substantially the fulllength of casing, to enhance overall heat extraction. Similarly, thechamber and the baffles may extend radially inwardly of the casing,towards the shaft, at the second end of the casing, to further enhanceheat extraction. However, this latter arrangement can complicate thefitting and electrical isolation of power supply to the motor, whichpreferably is at the second end. Thus, rather than provide for coolingat the second end, there preferably is an annular, fluid-tight sealbetween the casing and shell at the second end.

To enable the required flow of cooling fluid, inlet and outlet portsrelative for the chamber provide communication between the interior ofthe impeller sub-housing and the chamber. The inlet ports are providedat a higher pressure region of the impeller sub-housing, while theoutlet ports are provided at a lower pressure region of thatsub-housing, whereby a pressure differential prevailing in the impellersub-housing provides the force necessary to drive the cooling fluid intoand along the chamber from the first to the second end of the motorsub-housing, and then back to the first end for return to the impellersub-housing. Preferably the inlet ports are disposed radially outwardlywith respect to the outlet ports.

The number, size and radial location of the inlet and outlet portsenabling the flow of cooling fluid are chosen to satisfy a number ofconditions. A first condition is attainment of a sufficient pressuredifferential between the inlet and outlet ports to achieve a flow ofcooling fluid providing a suitable level of heat energy extraction fromthe motor casing for maintaining the motor at an efficient operatingtemperature. A second requirement is to ensure flow through each portwhich avoids undue generation of noise and vibrations. For the latterpurpose, the ports preferably are of a form free of sharp edges, whilethey also may have tubular extensions which project from a wall in whichthe ports are provided.

The flow of cooling fluid may be sufficient to enable the motor to bemaintained at an efficient operation temperature. However, the motorpreferably includes means for stirring or circulating air in the motorcasing around and through the motor, to assist in maintaining all partsof the motor at a relatively uniform temperature and, hence, to minimizegeneration of hot spots. The means for circulating the air may includeformations on the rotor coil and/or the rotor shaft which are shaped togenerate air circulation. The formations may be provided at one end ofthe motor to stir the air at one end of the motor, or air may be stirredby respective formations at each end of the motor. However, whereprovided at each end, the respective formations may co-operate bygenerating air flow in the motor casing, such as in each acting to causethe air to flow in one axial direction between the rotor and stator andin the opposite axial direction between the stator and the motor casing.

The impeller may be configured so as to co-operate with a surface of thesecond sub-housing to assist in maintaining the pressure differentialbetween the higher and lower pressure regions. For this purpose, theimpeller may have an annular spigot or fin which axially overlaps withand is closely adjacent to an annular spigot or fin of the secondsub-housing. However, instead of having a spigot or fin, one or each ofthe impeller and second sub-housing may have a stepped surface whichdefines an annular face which axially overlaps and is closely adjacentto an annular face, spigot or fin of the other. Such co-operationpreferably is between a transverse wall of the second sub-housing whichis adjacent to the first sub-housing and a face of the impeller opposedto the transverse wall.

The impeller, for the fluid pump of the second aspect, may be oneaccording to the first aspect. Preferably that impeller has inlet vanesas detailed above, while its second plate preferably may have an annularspigot or fin as detailed above. Where the impeller has such spigot orfin, the impeller is disposed in the impeller sub-housing with thespigot or fin of its second plate projecting towards and closelyadjacent to a partition wall which separates the sub-housings and inwhich the inlet and outlet ports are provided. The arrangement is suchthat the spigot or fin separates, or assists in separating, theabove-mentioned higher and low pressure regions of the impellersub-housing.

Where the impeller has a spigot or fin on its second plate separating orassisting in separating the pressure regions, the partition wall mayhave an annular spigot or fin which co-axially overlaps with theimpeller spigot or fin. The respective spigots or fins may be in slidingcontact in a manner not significantly retarding rotation of theimpeller. However, there preferably is a slight clearance between thespigots or fins, with this being such as to maintain the pressuredifferential between the higher and lower pressure regions. Also, insuch arrangement, the impeller may be of a form, as described above, inwhich the inner periphery of the second plate defines a clearance aroundthe shaft, and around any seal on the shaft adjacent to the secondplate. Thus cooling fluid, for controlling the operating temperature ofthe motor, is able to circulate along the motor casing as described, bypassing from a higher pressure region adjacent the outer periphery ofthe impeller, via inlet ports located radially outwardly of the spigotsor fins, and returning via the outlet ports, inwardly of the spigots orfins, so as to pass into the space between the impeller plates via thelower pressure region and the clearance.

As indicated above, the baffles may have lateral portions which extendto a central boss through which the shaft extends. The boss may extendbetween an end wall of the motor casing and an end wall of the outershell at the end of the sub-housing. The boss may be integral with theend wall of the shell. The end wall of the outer shell may comprise theabove-mentioned partition wall. However, an alternative arrangement ispreferred.

In the preferred arrangement, the first sub-housing has a transversevent which is located at the end of the first sub-housing adjacent tothe second sub-housing. The vent opens to one side, preferably to eachof opposed sides, of the first sub-housing and is located between arespective and wall of the outer-shell of the first sub-housing and ofthe motor casing. The vent is defined by the end wall of the outershell, a transverse pair of opposed side wall members and a transversebasal wall member which extends between the side wall members. The shaftextends from the motor casing between the side walls and through thebasal and end walls.

The end wall of the outer shell may comprise a partition wall whichseparates the sub-housings. In any event, a seal is provided on theshaft to at least minimize leakage of fluid along the shaft from thesecond sub-housing. The seal for this purpose may be housed in anannular spigot projecting axially from the outer shell end wall towardsor within the second sub-housing. With appropriate orientation of thefluid pump in use, the vent enables any fluid which does leak from thesecond sub-housing or from the chamber of the first sub-housing to drainunder gravity away from the shaft, thereby minimizing the risk of fluidpassing along the shaft to the motor housing. The appropriateorientation is with the shaft extending horizontally and the ventdisposed vertically and opening below the pump. Where the vent is openat each of its ends, it serves the added function of enablingair-circulation around the portion of the shaft extending across thevent.

The lower end of the vent preferably is plumbed to waste. This isdesirable, since recommended practice of mounting spa pumps in adrainage tray rarely is followed. In one form, a fitting such as anL-shaped connector is coupled to the lower end of the vent, to receiveany fluid passing into the vent, with a hose or conduit providingcommunication between the fitting and a drain pipe.

The side walls and the basal wall of the vent preferably are formedintegrally with the end wall of the outer shell of the firstsub-housing. The basal wall defines a central opening to enable theshaft to extend therethrough. Around that opening, at its face remotefrom the end wall of the outer shell, the basal wall may define anannular spigot with which a corresponding spigot on the end wall of themotor casing co-axially overlaps. A seal is provided between theoverlapping spigots, with the spigot of the basal wall preferablyreceiving therein the spigot of the casing end wall. Also, a bearing forthe shaft preferably is housed within the overlapping spigots.

In a third aspect of the present application, there is provided a fluidpump of the type described wherein the second sub-housing, having theimpeller therein, includes an inlet connector for coupling the pump to asupply conduit from a source of fluid to be pumped, and an outletconnector for coupling the pump to a return conduit. Each connectorcommunicates with the interior of the second sub-housing and is adaptedto provide releasable coupling to the respective conduit. For thispurpose, each connector defines a bore extending between the interior ofthe second sub-housing and an outer end of the connector. An end portionof the conduit for each connector is receivable in the bore, either as aneat sliding fit or with a slight clearance. At the outer end of eachconnector, the bore is of larger size to define a seat against which aresilient seal is locatable, around the conduit. A respective gland-typeof nut on each conduit is engageable with an external thread formed oneach connector such that, on tightening each nut, the respective seal isable to be compressed to secure the conduit in relation to the connectorand provide a fluid tight seal therebetween.

The connectors may be disposed with their bores extending insubstantially parallel relationship, an arrangement which allows thereto be some misalignment in the conduits, without leakage. The borespreferably are substantially parallel to the rotor axis. Mostconveniently, the connectors extend from the second sub-housing in adirection away from the first sub-housing. The outlet connectorpreferably communicates with the interior of the second sub-housing withits bore substantially in line with the outer periphery of the impeller.The bore of the inlet connector may be similarly aligned with the outerperiphery of the impeller. However, fluid flow from inlet connector tothe interior preferably is via a lateral opening from its bore such thatfluid passes to a central region of the impeller.

The fluid pump of the third aspect of the application may have thefeatures of a fluid pump according to the second aspect described above.That is, the first sub-housing containing the motor may be ofdouble-walled construction, with baffles within a chamber defined by thewalls of that sub-housing enabling the guidance of cooling fluid forcontrolling the operating temperature of the motor. Also, in line with apreferred form of the second aspect, the pump of the third aspectpreferably has an impeller according to the first aspect. Thus, there isenvisaged a fluid pump according to the third aspect which has animpeller according to the first aspect, with this pump preferably alsohaving features of the pump of the second aspect.

In each of the second and third aspect, the pump may include a heatingdevice in the first sub-housing by which cooling fluid circulatedtherethrough is able to be heated to a required degree. That is, inaddition to taking up heat energy from the motor, the fluid can befurther heated such as to maintain fluid circulated by the pump at arequired temperature level. The heater device may be mounted in themotor casing and, in one preferred form, it comprises a substrate of asuitable steel, such as stainless steel, with the substrate havingceramic overlay on which a heating element and control circuitry isprovided, such as by printing. Alternatively, such overlay, with theheating element and circuitry, may be formed directly onto the motorcasing.

The pump of the present invention may have an electrical enclosure atthe end of the first sub-chamber which is remote from the secondsub-chamber. That enclosure houses electrical components and terminalsby which electric power is supplied to the motor. The enclosure needs tobe isolated from the first sub-housing to prevent cooling fluid frompassing from the second sub-housing to the enclosure. Where the secondsub-housing is of double-walled construction provided by a motor casingand an outer shell, a seal, such as an O-ring seal, may be provided atthat remote end to provide a seal between the casing and shell, aroundan end wall of the second sub-housing at the remote end. However, therepreferably also is an annular channel, preferably integrally formed withthe end wall which co-operates with the casing and shell to form anannular drainage chamber which receives any fluid which passes the seal.At its lower extent, the chamber preferably has at least one drainageport from which fluid received in the chamber is able to discharge tothe exterior of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference now is directed to the accompanying drawings, in which:

FIG. 1 is an end elevation of a pump according to each of the second andthird aspects detailed above, incorporating an impeller according to thefirst aspect;

FIG. 2 is a sectional view of the pump, taken on line C-C II-II of FIG.1;

FIG. 3 is a similar view to FIG. 2, but is taken on line F-F III-III ofFIG. 1;

FIG. 4 is a perspective view of the impeller of the pump of FIG. 1;

FIG. 5 is a perspective view of the impeller shown in FIG. 4, but takenfrom the opposite axial end;

FIG. 6 is an internal perspective view of a housing component of thepump of FIG. 1;

FIG. 7 is an axial sectional view of a further embodiment of an impelleraccording to the invention;

FIG. 8 is a schematic representation of an axial sectional view of afurther embodiment of a pump according to the invention;

FIG. 9 is a view similar to FIG. 6, but in respect of a housingcomponent of the pump of FIG. 8;

FIG. 10 is a perspective view of detail of the housing of FIG. 9;

FIG. 11 is a sectional view of the detail shown in FIG. 10;

FIG. 12 is a perspective view from one end of a motor casing for use ina pump according to the invention, showing a first modified arrangement;

FIG. 13 is similar to FIG. 12, but is in respect of a motor casingshowing a second modified arrangement enabling heating of water; and

FIG. 14 is a sectional view of the casing of FIG. 13, showing the secondmodified arrangement enabling heating in relation to a pump motor.

DETAILED DESCRIPTION OF THE INVENTION

Referring first to FIGS. 1 through 3, the pump 10 shown therein has afirst sub-housing 12 in which an electric motor 14 is mounted, and asecond sub-housing 16 in which an impeller 18 is mounted on a rotorshaft 20 of motor 14. The sub-housings 12, 16 are axially in-line. Alsothe pump 10 is of cylindrical form overall. However, as can beappreciated from FIG. 1, sub-housings 12 and 16 are coupled together bybolts 22 through respective rectangular end flanges 12 a and 16 a.Flange 16 a provides a first stand on which the pump 10 is supportablein its in-use orientation shown in FIG. 2, while the remote end ofsub-housing 12 has a bracket 12 b for further supporting pump 10 in thatorientation.

The sub-housing 12 includes an inner motor casing 24 in which motor 14is located, and an outer shell 26. The casing 24 is of metal, preferablyof good thermal conductivity, and conforms relatively closely to theform of motor 14. Thus a cylindrical central section 24 a of casing 24conforms closely to the external form of the stator 27 of motor 14.Also, casing 24 at each end 24 b thereof defines an axially extendingspigot 24 c through which rotor shaft 20 of motor 14 extends. Shaft 20is journalled in a respective bearing 28 mounted in each spigot 24 c.

Outer shell 26 of sub-housing 12 may be of any suitable material, butpreferably is of a suitable plastics material. Shell 26 is of two partconstructions providing a main part 30 and an end cap 31 which interfita short distance beyond bracket 12 b. As shown, the interfittherebetween is around the adjacent end of region 24 b of casing 24, andprovides accommodation for a resilient O-ring seal 32 which seals theinterior of cap 31 from the interior of main part 30.

As indicated later herein, cooling fluid is circulated through chamber34 to control the operating temperature of motor 14. The seal 32isolates the interior of cap 31 from the interior of the main part 30 ofsub-housing 12. However, given that presence of cooling fluid, thejunction of cap 31 and shell 26 of sub-housing 12 defines a channel 33into which is received any fluid which passes seal 32. The channel 33 isof annular form, with the opening of that form upper-most, such that itis visible only in the lower part of each of FIGS. 2 and 3. The channel33 is defined by concentric flanges 31 a and 31 b of cap 31 which bridgeseal 32 and provide a seal thereacross. Fluid, such as water, receivedinto channel 33 is able to drain under gravity to the lower extent ofchannel 33, and then is able to drain exteriorly of pump 10 throughdrain hole 33 a.

The main part 30 of shell 26 has a cylindrical peripheral wall 30 a.Also, extending across the end of wall 30 a adjacent to sub-housing 16,shell 26 has an end wall 30 b which provides a partition betweensub-housings 12 and 16. Wall 30 a is spaced radially outwardly fromsection 24 a of motor casing 24, while end wall 30 b is spaced axiallybeyond the adjacent end 24 b of casing 24. Thus a chamber 34 is definedbetween part 30 and casing 24 which extends axially from seal 32 towardssub-housing 16 and, adjacent to sub-housing 16, radially inwardlybetween end wall 30 b and the adjacent end 24 b of casing 24.

As shown most clearly in FIG. 2, the main part 30 of shell 26 defines avertical vent 36 which is open at the top and bottom of sub-housing 12.The vent 36 is formed by end wall 30 b, a parallel pair of transversewalls 38 and, joining edges of walls 38 remote from wall 30 b, atransverse wall 40 which is substantially parallel to wall 30 b. Thevent 36 is open at its ends by virtue of respective openings 36 a inmain part 30 of shell 26.

From the end of motor casing 24 nearer to second sub-housing 16, therotor shaft 20 extends through opening 40 a in wall 40. Beyond opening40 a, shaft 20 extends between walls 38 from each of which it is spaced,and through opening 41 in end wall 30 b into sub-housing 16. As shown,walls 38 and 40 are formed integrally with main part 30 of shell 26, asis a spigot 42 which projects from the surface of wall 40 remote fromwall 30 b. The spigot 42 is co-axial with opening 40 a, and receivestherein the end spigot 24 c of casing 24 which is nearer to sub-housing16. The inner circumference of spigot 42 is stepped, to accommodate aresilient O-ring seal 43 therein, around that spigot 24 c.

FIG. 6 shows the interior of main part 30 of outer shell 26, from theend of part 30 to which end cap 31 is to be interfitted. As seen mostclearly in FIG. 6, part 30 has a circumferentially spaced array ofbaffles 44 formed integrally therewith. Each baffle 44 is of L-shape,and has a stem portion 44 a which extends along a major part of thelongitudinal length of wall 30 a of part 30 and which is disposed in arespective radial plane of part 30. Each baffle 44 also has a headportion 44 b which projects axially from wall 30 b and which has alarger radial extent in the same plane as its stem portion 44 a. Eachstem portion 44 a extends radially from wall 30 a to section 24 a ofmotor casing 24. Also, each head portion 44 a extends axially to the end24 b of casing 24 nearer to sub-housing 16 and radially to the nearerone of walls 38. The baffles 44 thus sub-divide chamber 34 into acircumferential array of segments. However alternate stem portions 44 aare shorter than their next adjacent neighbours such that successivepairs of the segments of chamber 34 are in communication adjacent theend of wall 30 a remote from sub-housing 16.

Wall 30 b of shell 26 has a peripheral skirt 46 which projects axiallyaway from casing 24. The sub-housing 16 has a cylindrical peripheralwall 48 which, adjacent to sub-housing 12, has an open end which isreceived in skirt 46. Wall 30 b thus forms a common partition wallbetween the sub-housings 12 and 16. At the other end of wall 48,sub-housing 16 has a transverse end wall 50. The sub-housing 16 definesa chamber 52 and providing communication with chamber 52, sub-housing 16has an inlet connector 54 and an outlet connector 55. As shown,connectors 54 and 55 extend axially beyond wall 50, away fromsub-housing 12, in diametrally opposed, parallel relationship.

The impeller 18 is mounted on and is rotatable with shaft 20 of motor14, within chamber 52 of sub-housing 16. The impeller 18 is axiallylocated within the open end of skirt 48 of sub-housing 16, adjacent towall 30 b. At the axial side of impeller 18 remote from sub-housing 12,chamber 52 is sub-divided by a part cylindrical skirt 56 and apenannular flange 58. The skirt 56 is integral with end wall 50 ofsub-housing 16 and extends axially therefrom over part of the axialextent of skirt 48. The skirt 56 is part cylindrical since it defines anopening 56 a which is in line with inlet connector 54. The flange 58 isintegral with skirt 48 and skirt 56 and, while flange 58 extends acrossopening 56 a, it has an opening 58 a between its ends which is axiallyin line with outlet connector 55. Also, as shown, flange 58 is ofshallow, somewhat frusto-conical form so as to be substantially parallelto an axially opposed surface of impeller 18 in radial directions.However, flange 58 has the form of a volute and, circumferentially, itvaries in displacement away from the axially opposed surface of impeller18 at a constant pitch angle.

The impeller 18 has a first annular plate 62 which is of shallow,frusto-conical form and, axially spaced from plate 62, it has a secondannular plate 64. While plate 64 is flat over a major part of its widthwhich is axially in-line with plate 62, it has an inner margin 64 awhich is turned slightly, in the axial direction of plate 62. Betweenplates 62 and 64, impeller 18 has a series of circumferentially spacedvaries 66. The varies 66 are arcuate, so as to extend outwardly in aspiral array.

Within and spaced from the inner periphery of plate 62, impeller 18 hasa central hub 68. A circumferential array of connectors, comprisingvanes 70, secure plate 62 in relation to hub 68. In the arrangementshown, the vanes 70 are generally disposed in a plane perpendicular toshaft 20, although they can be inclined slightly with respect to suchplane, while each vane 70 has its free edges relatively axiallydisplaced with respect to that plane. With rotation of impeller 18,vanes 70 may be operable to assist axial flow of fluid, although vanes70 may be neutral with respect to such flow.

Around the junction of vanes 70 with the inner periphery of plate 62,impeller 18 has a skirt 72 which projects axially away from plate 64.The skirt 72 is within and only slightly spaced from an end portion ofskirt 56 remote from end wall 50 of sub-housing 16.

The hub 68 of impeller 18 has a central boss 69 which defines a bore 69a by which impeller 18 is mounted on shaft 20. Around boss 69, hub 68has a concentric skirt 71, with boss 69 and skirt 71 merging at adome-shaped end 68 a of hub 68 which is axially beyond plate 62 in adirection away from plate 64. As shown, the skirt 71 extends axiallybeyond boss 69 towards wall 30 b of part 30 of shell 26. Within skirt71, there is received an end of a seal 74 provided on shaft 20 withinchamber 52. The other end of seal 74 bears against wall 30 b, aroundopening 41, and is received within an annular spigot 76 integral withwall 30 b and projecting axially towards impeller 18.

Radially outwardly beyond spigot 76, wall 30 b has a further annularspigot 78 which is integral therewith and projects axially towardsimpeller 18. The spigot 78 has an internal diameter which is slightlygreater than the spacing between the respective external surface ofwalls 38, as seen most clearly in FIG. 3. Also, the spigot 78 axiallyoverlaps with, and is closely adjacent to, an annular spigot 80 which isintegral with second plate 64 of impeller 18 and which projects axiallyaway from first plate 62, towards wall 30 b.

A principal aspect of operation of pump 19 now will be described. Forthis, it is assumed that inlet connector 54 is coupled to a conduit froma supply outlet of fluid, such as water, which is to be pumped;connector 55 is coupled to a return conduit for the fluid, and thatmotor 14 is operating to rotate impeller 18. With that operation, fluidenters a bore 81 defined by inlet connector 54, and flows in chamber 52inwardly across flange 58 and through opening 56 a of skirt 56. In theportion of chamber 52 within skirt 56, the fluid is presented across thedomed end of 68 a of hub 68 and flows axially through the array of vanes70 into the space between plates 62 and 64 of impeller 18. From thatspace, the fluid is forced by the vanes 66 between the plates 62 and 64,so as to be forcefully pumped outwardly between the outer periphery ofplates 62 and 64. Beyond, the outer periphery of plates 62 and 64, thefluid is constrained to flow around an annular, relatively high pressureregion 52 a of chamber 52, defined by wall 30 b, flange 58 and theportion of wall 48 therebetween. From region 52 a, the fluid dischargesunder the prevailing high pressure through opening 58 a in flange 58,and then via a bore 83 defined by outlet connector 55.

In the description of the principal aspect of operation of pump 10, theflow of pumped fluid is facilitated principally by the action of vanes66. Vanes 70 may assist slightly to force the fluid axially, althoughthe principal function of vanes 70 is as connectors securing plate 62 tohub 68 and, hence, in relation to plate 64. The vanes 66 act to spiralthe fluid outwardly away from a central region 52 b adjacent to the freeend of skirt 71 of hub 68. While fluid in that central region 52 btherefore is pressurised, the region 52 b is one low pressure relativeto that in region 52 a.

Between second plate 64 of impeller 18 and wall 30 b, the pressuresprevailing in regions 52 a and 52 b are substantially isolated. This isdue to the closely adjacent, axially overlapping spigots 78 and 80 ofwall 30 b and plate 64, respectively. This substantial isolation enablesa second aspect of operation of pump 10 by which some of the fluid beingpumped is circulated through chamber 34 to control the operatingtemperature of motor 14. For this, there is formed in wall 30 b anangularly spaced array of radially outer openings 82 (see FIGS. 3 and6), and also an angularly spaced array of radially inner openings 84(see FIGS. 2 and 6).

The respective arrays of openings 82 and 84 provide communicationbetween chamber 52 of sub-housing 16 and chamber 34 within sub-housing12. As shown in FIG. 6, the array of openings 82 is angularly offsetfrom the array of openings 84. The arrangement is such that thecommunication is via a respective one of openings 82 and 84 for each ofthe sectors of chamber 34 defined by baffles 44, with the communicationfor each alternate sector being via a respective opening 82 and that foreach other, adjacent sector via a respective opening 84. Thus, some ofthe liquid in the relatively high pressure region 52 a is able to passthrough each opening 84 into the respective alternate sectors for whichthose openings provide communication. From the openings 82, the fluid isable to circulate between the heads 44 b, and longitudinally between thelegs 44 a, of the baffles 44 defining those alternate sectors. Thelongitudinal flow continues to the end of shell 26 remote from thesub-housing 16. As one of the legs 44 a for each of the alternatesectors is shorter than the other, the fluid is able to flow around theremote end of the shorter leg 44 a and to flow back towards sub-housing16 in an adjacent sector. The return flow of fluid passes radiallybetween the heads 44 b of the baffles 44 defining each of the adjacentsectors, and passes through the respective opening 84 to the relativelylow pressure region 52 b.

The flow of fluid through the sectors of chamber 34 maintains the fluidin good thermal contact with the casing 24 of motor 14. Thus excess heatenergy generated by motor 14 is able to be extracted by the fluid,through casing 24 over substantially the full axial length of centralsector 24 a of casing 24, as well as from the end 24 b of casing 24which is nearer to sub-housing 16. The size of openings 82 and 84 isselected to achieve a required flow rate of fluid through the sectorswhereby the operating temperature of motor 14 is able to be controlledto a suitable level. Thus, overheating of motor 14 is able to beavoided, while it is able to be maintained at a temperature appropriatefor its efficient operation.

As indicated, the connectors 54 and 55 are in diametrically opposed,parallel relationship. As shown in FIGS. 2 and 3, the respective bore 81and 83 of connectors 54 and 55 is enlarged at its outer end 81 a and 83a to define a frusto-conical seat 81 b and 83 b. Also, each connectionis externally threaded, as shown at 81 c and 83 c, respectively. In eachcase, the arrangement is such that a respective conduit can bereleasably coupled to each of the connectors. Thus, as shown in FIG. 3for outlet connector 55, the conduit 83 d is received with a neat fitwithin bore 83, beyond the seat 83 b. A seal 89 on conduit 83 d then isin position against the seat 83 b. A nut 91, having a trailingperipheral flange 91 a then is tightened onto the thread 86 c, tocompress the seal 89 into a fluid-tight fit between connector 55 and itsconduit 83 d. The situation is the same for inlet connector 54 and itsconduit (not shown).

In FIG. 3, nut 91 is shown as tightened. Thus seal 89 illustrates itscompressed form. In its uncompressed condition, the seal has across-section which has the form of a tetragon with parallel inner andouter sides and, at its axial ends, a respective side which iscomplementary to the opposed face of seat 83 b and the inner face offlange 91 a. As the nut 91 is tightened, seal 89 is axially compressed,thereby urging its outer surface into a fluid-tight engagement withinend 83 a of bore 83 and its inner surface into fluid-tight engagementwith conduit 83 d. Again, the situation is the same for the seal forinlet connector 54 and its conduit.

The pump 10 has a number of practical benefits. One of these is theoverall compact design. A feature enabling this is the form of impeller18 which enables seal 74 to be recessed therein. As seal 74 issubstantially within the axial extend of impeller 18, it is able to beof a suitable axial length for efficient sealing or shaft 20 withoutsignificantly increasing the axial extent of pump 10.

A further practical benefit of pump 10 is provided by vertical vent 36.This enables any fluid which passes seal 74 from chamber 52 to drain outof sub-housing 12, substantially eliminating the risk of the fluidpassing to and through the adjacent bearing 28 and into casing 24. Also,air is able to circulate through vent 36, thereby enabling the sectionof shaft 20 in vent 26 to be kept substantially dry. However, the vent36 preferably is plumbed to waste at its lower end.

The form of impeller 18 facilitates attainment of an efficient pumpingaction. The interaction of impeller 18 with sub-housing 16 enhancesthis, while that interaction also enables fluid flow for control of theoperating temperature of motor 14. Thus, for example, a close fitting ofskirt 72 of impeller 18 within the end section of skirt 56 facilitatesthe flow of fluid within skirt 56 being drawn through rather than aroundskirt 72. This may be assisted by the action of vanes 70, butprincipally is due to the higher pressure prevailing in region 52 arelative to region 52 b. Similarly, the close inter-fitting betweenspigot 78 of wall 30 b and spigot 80 of impeller 18 enables maintenanceof a sufficient pressure differential between regions 52 a and 52 b. Itis not necessary that skirt 72 being in contact with the end portion ofskirt 56, or for spigots 78 and 80 be in contact. Indeed, given thatimpeller 18 is to rotate, wear would result in loss of such contact,while manufacturing tolerances would make difficult the attainment ofsuitable sliding contact. Rather, the respective fittings are to be suchas to generate sufficient resistance to flow as to ensure flow thoughskirt 72 and maintenance of the pressure differential. The pressuredifferential and the provision of openings 82 and 84 in wall 30, enableefficient flow of fluid into chamber 34 for control of the operatingtemperature of motor 14.

Turning now to FIG. 7, the impeller 118 shown therein has an overallform corresponding to that of impeller 18 shown in FIGS. 2 to 5. Theparts of impeller 118 corresponding to those of impeller 18 have thesame reference numeral, plus 100. Thus, impeller 118 has first annularplate 162, axially spaced from second annular plate 164. Between plates162 and 164, impeller 118 has a series of circumferentially spaced vanes166 which are arcuate and extend outwardly in a spiral array. The vanes166 partially overlap such that the outer end of one is spaced radiallyoutwardly from the inner or leading end of a next vane. Also, in thisinstance, the vanes 166 are formed integrally with plate 164 and abutthe nearer surface of plate 162.

Within and spaced from the inner periphery of plate 162, impeller 118has a central hub 168. Radial connectors in the form of vanes 170,inclined slightly from a plane perpendicular to the axis of impeller118, secure plate 162 in relation to hub 168. Vanes 170 are at leastneutral with respect to initial axial flow of fluid on rotation ofimpeller 118. As shown, an annular skirt 172 projects from the innerperiphery of plate 162, away from plate 164. The vanes 170 join hub 168to plate 162 via the skirt 172. The hub 168 has a central boss 169 whichdefines a threaded bore 169 a by which impeller 118 is mountable on amotor output shaft for rotation therewith. Around boss 169, hub 168 hasa concentric skirt 171, with hub 168 and skirt 171 merging at domed end168 a.

The boss 169, unlike other structure of impeller 118 in the plane ofFIG. 7, is shown unshaded. This is because, in the arrangement shown,boss 169 is split in that plane to define two portions, each ofsubstantially semi-cylindrical form, although such split need not beprovided. The outer surface of each portion defines a peripheral ledge85 for use in securing plate 164 in relation to plate 162. For thissecurement, the inner periphery of plate 164 is turned to define anannular skirt 164 a from the end of which a plurality of hooked fingers86 project away from plate 164. The outer surface of boss 169 tapersinwardly from ledges 85, in a direction away from end 168 a such that asplate 164 is presented axially towards plate 162, the fingers 86 areable to ride over that surface to locate their hooked ends 86 a behindledges 85. The portions of boss 169 are able to flex towards each other,while the fingers 86 also are able to flex outwardly to facilitate thisengagement. On attaining that engagement, skirts 171 and 164 a arebrought into and held in end to end abutting relationship as shownwhile, as indicated above, vanes 166 on plate 164 abut against plate162.

The arrangement of impeller 118 is such that, while it overall is ofcomplex form, it is readily able to be assembled from two parts each ofmore simple form. Also, the snap engagement between fingers 86 and boss169 obviates the need for a further operation involved with the frictionwelding used for the components of impeller 18 of FIGS. 2 to 5.Moreover, while separation of the components of impeller 118 can bedifficult, at least without special tools, separation is not likely tobe necessary.

The pump 110 of FIG. 8 in large part is similar to pump 10 of FIGS. 1 to3. Corresponding parts have the same reference numeral, plus 100. Thus,pump 110 has a first sub-housing 112 in which electric motor 114 ismounted and a second sub-housing 116 in which an impeller 118 is mountedon rotor shaft 120 of motor 114. The impeller 118 is as shown in FIG. 7,although it could be of the form of impeller 18 of FIGS. 2 to 5.

The coupling between sub-housings 112 and 116 differs in that it is ofannular form. Also, sub-housing 112 has a thickened flange 112 a withinwhich impeller 118 is located and which is received within steppedflange 116 b of sub-housing 116. Also, at its other end, sub-housing isnot provided with a support bracket (corresponding to bracket 12 b shownin FIG. 2). Rather, a support bracket 131 a is provided with end cap 131such that pump 110 is able to stand on bracket 131 a and bracket 116 aof sub-housing 116.

In most other respects, pump 119 as shown in FIG. 8 is similar to pump10 of FIGS. 1 to 3. However, for ease of illustration, some structure ofsub-housing 112 between outer shell 126 and motor casing 124 is notshown, although it is similar to that described with reference to pump10 of FIGS. 1 to 3. Thus, while not shown, sub-housing 112 includes avertical vent, corresponding to vent 36, while fluid flow betweenbaffles 144 is enabled by openings corresponding respectively toopenings 82 and 84 of pump 10 of FIGS. 1 to 3, as shown by openings 182and 184 in FIG. 9. Thus pump 119 enables circulation of cooling water,to extract heat energy from motor 114, in essentially the same manner aswith motor 10.

As with motor 10 of FIGS. 1 to 3, pump 110 enables heat energyextraction from the full axial extent of the peripheral wall 124 a ofcasing 124 as well as from the end wall 124 b of casing 124 nearer tosub-housing 116. In general, this is sufficient to control the operatingtemperature of motor 114. To the extent that this is not the case, pump110 provides for further cooling at the end of motor 114 remote fromsub-housing 116.

For the further cooling, pump 110 includes means 87 on the rotor, at theend of motor 114 remote from sub-housing 116 (but optionally at eachend) for circulating air within casing 124 around and through motor 114.In the arrangement shown, the means 87 comprises a castellated formationon the end of the rotor core 88. However, means 87 could comprise finsor the like on rotor shaft 120. In each case, the means 87 functions toeliminate possible hot-spots by heat energy being taken up bycirculating air and thereby facilitating maintenance of a relativelyuniform temperature in all parts of motor 114. If required, ventscommunicating between the interior of motor casing 124 and the interiorof end cap 131 can be provided in the end wall 124 b adjacent to cap 31,to enable fresh cooling air to be drawn into casing 124 from end cap131.

For ease of illustration, FIG. 9 shows only selected detail on the outershell 126 of sub-housing 112 of rotor 110. The detail is in relation toend wall 130 b of shell 126. Thus not shown, for example, are bafflescorresponding to baffles 44 of outer shell 26 of motor 10 of FIGS. 1 to3.

As shown in FIG. 9, end wall 130 b has radially outer openings 182 andradially inner openings 184 therethrough. These provide communicationbetween respective high and low pressure regions of the chamber 152 ofimpeller housing 116 and the interior of shell 126 to enable circulationof cooling water around motor casing 124. Thus, the operatingtemperature of motor 114 is able to be controlled in the same manner asdescribed in relation to motor 14 of pump 10 of FIGS. 1 to 3.

The radial location, number, and size of openings 182 and 184 isselected to provide a required flow rate of cooling water around motorcasing 124 appropriate for maintaining a sufficient level of heat energyextraction from casing 124. Also, the shape of openings 182 and 184 isselected so as to minimise noise generated by water flow therethrough.As shown in FIG. 9, the openings are of circumferentially elongate form.Also, the openings 182 and 184 are axially elongated by provision ofshort, tubular extensions 182 a and 184 a as shown in detail in FIGS. 10and 11 for openings 182. The extensions 182 a and 184 a are formedintegrally with wall 130 b. In the arrangement shown, each extension 182a and 184 a projects within shell 126, although they all may extend intochamber 152. Alternatively, if required, openings 182 a may extendoppositely to openings 184 a, but with openings 182 a most preferablyextending within shell 126.

As also shown in FIG. 9, a vent hole 89 is provided in the upper extentof wall 130 b. Thus, air in shell 126 on start-up of pump 110 is able tobe displaced into the vertical vent (not shown, but corresponding tovent corresponding to vent 36 of FIGS. 2 and 3).

The flange 116 a and bracket 131 a are such that, with pump 110 standingon a horizontal support surface, the axis of pump 110 is inclineddownwardly at a small angle to the horizontal, such as at an angle ofabout 3°, towards sub-housing 116. This enables water in pump 110 todrain out after motor 114 has been turned off. To facilitate drainage ofwater from shell 126, drainage holes 90 are provided in the lower extentof wall 130 b. Thus, water in shell 126 is able to flow back intochamber 152, with air returning to shell 126 via vent hole 89. Alsowater in chamber 152 is able to drain via outlet bore 183.

The arrangement of pump 10 of FIGS. 1 to 3 (and of pump 110 of FIG. 8)is intended to extract heat energy from motor casing 24 (124). By thismeans, the temperature of motor 14 (114) is prevented from building up,and the operating temperature of the motor is able to be controlled. Theheat energy is taken up by the water circulated from the impellerchamber 52 (152), through shell 26 (126) and then back through chamber(52 (152) before being discharged from pump 10 (110). Where, forexample, the pump is utilized to provide recycling of water to the jetsof a spa bath, heating of water discharged from the pump can be ofbenefit in maintaining the bath temperature at a suitable level. Indeed,there can be benefit in increasing the level of heat energy taken up bythe recycled water, and FIG. 12 shows an arrangement suitable for this.

FIG. 12 shows an internal perspective view of a first modifiedarrangement for motor casing 124 for pump 110 (although a similarmodification is possible for casing 24 of pump 10). The view of FIG. 12is from the end of casing 124 at which end cap 131 of sub-housing 116 issecured. While having a generally cylindrical central section 124 a,casing 124 is modified to enable a heater device 91 to be fittedtherein. As shown, a part of section 124 a is pressed outwardly todefine a longitudinally elongate, rectangular recess 92 in which device91 is mounted. The device 91 comprises a stainless steel substratehaving a ceramic overlay on which a strip heating element withassociated electronic control circuitry is provided, such as by screenprinting. Thus, additional heat energy is able to be generated at, andtransferred to, the part of casing section 124 a at which recess 92 isdefined. Control of the additional heat energy level enables regulationof the total heat energy level able to be taken up by the circulatedwater. Thus a body of water in the spa bath, for which pump 110 is beingused to recycle water to jets of the spa bath, is able to be maintainedat a required temperature level.

FIGS. 13 and 14 show internal perspective views of a second modifiedarrangement for motor casing 124 of pump 110 (although, again, a similarmodification is possible for casing 24 of pump 10). In FIG. 13, thecasting 124 is shown without motor 114. However, FIG. 14 shows motor114, its shaft 120, rotor core 88 and stator 88 a in schematic outline.

FIGS. 13 and 14 differ from FIG. 12 in the type and form of heatingelement provided. Rather than the arrangement of FIG. 12, FIGS. 13 and14 show a resistance heating element 94 which extends around thejunction of cylindrical wall 124 a of casing 124 and its end wall 124 bwhich, in pump 100, is adjacent to sub-housing 116. The junction ofwalls 124 a and 124 b define an annular channel 95 in which element 94is received in good surface to surface contact to facilitate thetransfer of heat energy from element 94, through the thickness of casing124 defining channel 95, to water circulating over the external surfaceof casing 124. As seen most clearly in FIG. 13, heating element 94 isformed from an elongate resistance heating material 94 a housed in anelectrically insulating sheath 94 b. Element 94 is of substantiallytoroidal form to fit in channel 95, with respective ends 94 c of heatingmaterial 94 a adjacent and projecting axially for connection to powersupply leads (not shown). The power supply leads extend axially withincasing 124, between wall 124 a and stator 88 a, and through the end (notshown) of casing 124 remote from element 94 to power supply terminals(not shown but corresponding to terminals 96 a of power supply component96 shown in FIG. 8). The component 96 supplies electric power foroperating motor 114, as well as for heating element 94.

As will be appreciated, maintenance of the temperature of the body ofwater of a spa bath necessitates only sufficient heat energy to offsetnatural cooling of the water. With a motor having a power rating of 500W, a substantial part of this requirement is available from heat energygenerated by the motor in excess of that necessary for maintenance ofthe motor at an efficient operating temperature, particularly given thatpumps usually are mounted in an enclosure. Indeed, providing adequateventilation for the pump usually is a problem. However, with take-up ofthat excess heat energy by circulating water, further heating formaintenance of water temperature by the heating device can be relativelyminor and, particularly where this is the case, the control circuitryfor the heating device can be operable to power the device only asrequired to maintain the circulating water within a predeterminedtemperature range.

With a system supplying heated water, it is a normal requirement for thesystem to have a thermostat controlling maximum permissible watertemperature, such as to a level of 40° C. for example. However, despitethe provision of a thermostat for this purpose, it is possible for waterin the pump to exceed that level substantially, despite power to thepump being cut-off, due to the substantial heat energy capacity of themotor. To safeguard against the pump being re-started while holdingover-heated water, there preferably is a second thermostat whichdisables the pump, so as to necessitate its resetting, if a secondtemperature, such as 50° C. is exceeded. Where a heater device isprovided, its circuitry may include a switch by which both the pump andthe heater device are resettable after sufficient cooling of over-heatedwater in the pump.

Finally, it is to be understood that various alterations, modificationsand/or additions may be introduced into the constructions andarrangements of parts previously described without departing from thespirit or ambit of the invention.

1. A fluid pump of the type in which a housing assembly has a firstsub-housing having an electric motor therein which is in line with asecond sub-housing having an impeller therein, with the motor having arotor shaft which extends through a seal of the first sub-housing intothe second sub-housing and with the impeller mounted on the rotor shaftso as to be rotatable by the motor, and the second sub-housing havinginlet and outlet ports through which fluid, such as water, is able to bepumped through the second sub-housing: wherein the first sub-housingcontaining the motor is of double-walled construction enabling fluidcooling of the motor, with the double-walled construction provided by amotor casing which houses a stator and the rotor shaft of the motor andby an outer shell spaced from and enclosing the motor casing; wherein,within a chamber of the first sub-housing defined between the casing andshell, there is provided a plurality of elongate baffles for guidingcooling fluid for flow over a major part of the external surface of thecasing whereby the operating temperature of the motor is able to becontrolled by heat energy extracted by the fluid from the casing;wherein the baffles are of a form providing for a flow of cooling fluidalong substantially the full axial length of the motor casing; whereinthe baffles provide flow from a first end of the first sub-housingadjacent to the second sub-housing, along the casing to its second endand then back along the casing to the first end by there beingalternating longer and shorter baffles, with the longer bafflesextending substantially to the second end of the casing and the shorterbaffles terminating short of the longer baffles at that second end,whereby cooling fluid is able to flow to the second end of the casingbetween alternate pairs of baffles, and then pass around the end of eachshorter baffles of each pair for return flow to the first end of thecasing between next adjacent pairs of baffles; and wherein the firstsub-housing has a transversely extending drainage vent which is locatedat the end of the first sub-housing adjacent to the second sub-housing,the vent extends from the shaft and opens to at least one of opposedsides of the first sub-housing and is located between a respective endwall of the outer-shell of the first sub-housing and of the motorcasing, and the transverse extent of the vent is defined by the end wallof the outer shell, a transverse pair of opposed side wall members and atransverse basal wall member which extends between the side wallmembers, and the shaft extends from the motor casing between the sidewall members and through the basal wall member and the end wall.
 2. Thepump of claim 1, wherein the second sub-housing includes an inletconnector for coupling the pump to a supply conduit from a source offluid to be pumped, and an outlet connector for coupling the pump to areturn conduit; each connector communicates with the interior of thesecond sub-housing and is adapted to provide releasable coupling to therespective conduit in which: (i) each connector defines a bore extendingbetween the interior of the second sub-housing and an outer end of theconnector; (ii) an end portion of the conduit for each connector isreceivable in the bore, either as a neat sliding fit or with a slightclearance; (iii) at the outer end of each connector, the bore is oflarger size to define a seat against which a resilient seal islocatable, around the conduit; and (iv) a respective gland-type of nuton each conduit is engageable with an external thread formed on eachconnector such that, on tightening each nut, the respective seal is ableto be compressed to secure the conduit in relation to the connector andprovide a fluid tight seal between the conduit and the connector.
 3. Thepump of claim 2, wherein the connectors are disposed with their boresextending in substantially parallel relationship whereby somemisalignment in the conduits, without leakage, is allowed.
 4. The pumpof claim 2, wherein the bores are substantially parallel to the rotoraxis, and the connector extend from the second sub-housing in adirection away from the first sub-housing.
 5. The pump of claim 2,wherein the outlet connector communicates with the interior of thesecond sub-housing with its bore substantially in line with the outerperiphery of the impeller.
 6. The pump of claim 2, wherein the bore ofthe inlet connector is aligned with the outer periphery of the impeller,and fluid flow from inlet connector to the interior of the secondsub-housing is via a lateral opening from the bore of the inletconnector such that fluid passes to a central region of the impeller. 7.The pump of claim 1, wherein the baffles are of a form providing for aflow of cooling fluid along substantially the full axial length of themotor casing.
 8. The pump of claim 1, wherein at the first end of thefirst sub-housing the chamber of the first sub-housing, defined betweenthe casing and the shell, extends radially inwardly from the shelltowards the rotor shaft, across an end of the casing adjacent to thefirst end of the first sub-housing.
 9. The pump of claim 8, wherein thebaffles have lateral portions which extend across the end of the casingfrom their main longitudinal extent to a central boss through which theshaft extends, whereby the cooling fluid is able to extract heat energyfrom the casing at the first end, as well as from substantially the fulllength of casing, to enhance overall heat extraction.
 10. The pump ofclaim 9, wherein the chamber and the baffles extend radially inwardlyfrom the shell, towards the shaft, across an end of the casing adjacentto the second end of the casing, to further enhance heat extraction. 11.The pump of claim 1, wherein the flow of cooling fluid is enabled by aplurality of inlet and a plurality of outlet ports for the chamber whichprovide communication between the interior of the impeller sub-housingand the chamber, with the inlet ports provided at a higher pressureregion of the impeller sub-housing and the outlet ports provided at alower pressure region of that sub-housing, whereby a pressuredifferential prevailing in the impeller sub-housing provides a forcenecessary to drive the cooling fluid into and along the chamber from thefirst to the second end of the motor sub-housing, and then back to thefirst end for return to the impeller sub-housing.
 12. The pump of claim11, wherein the inlet ports are disposed radially outwardly with respectto the outlet ports.
 13. The pump of claim 11, wherein the ports are ofa form free of sharp edges and have tubular extensions which projectfrom a wall in which the ports are provided.
 14. The pump of claim 1,wherein the motor includes means for stirring or circulating air in themotor casing around and through the motor, to assist in maintaining allparts of the motor at a relatively uniform temperature and, hence, tominimize generation of hot spots.
 15. The pump of claim 14, wherein themeans for stirring or circulating the air include formations on a rotorcoil of the motor and/or the rotor shaft which are shaped to generateair circulation.
 16. The pump of claim 15, wherein the formations areprovided at at least one end of the motor to at least stir air at the atleast one end of the motor.
 17. The pump of claim 16, wherein theformations are provided at each end of the motor and the respectiveformations co-operate by generating air flow in the motor casing tocause the air to flow in one axial direction between the rotor andstator and in the opposite axial direction between the stator and themotor casing.
 18. A fluid pump of the type in which a housing assemblyhas a first sub-housing having an electric motor therein which is inline with a second sub-housing having an impeller therein, with themotor having a rotor shaft which extends through a seal of the firstsub-housing into the second sub-housing and with the impeller mounted onthe rotor shaft so as to be rotatable by the motor, and the secondsub-housing having inlet and outlet ports through which fluid, such aswater, is able to be pumped through the second sub-housing: wherein thefirst sub-housing containing the motor is of double-walled constructionenabling fluid cooling of the motor, with the double-walled constructionprovided by a motor casing which houses a stator and the rotor shaft ofthe motor and by an outer shell spaced from and enclosing the motorcasing; wherein within a chamber of the first sub-housing definedbetween the casing and shell, there is provided a plurality of elongatebaffles for guiding cooling fluid for flow over a major part of theexternal surface of the casing whereby the operating temperature of themotor is able to be controlled by heat energy extracted by the fluidfrom the casing; wherein the baffles are of a form providing for a flowof cooling fluid along substantially the full axial length of the motorcasing; wherein the baffles provide flow from a first end of the firstsub-housing adjacent to the second sub-housing, along the casing to itssecond end and then back along the casing to the first end by therebeing alternating longer and shorter baffles, with the longer bafflesextending substantially to the second end of the casing and the shorterbaffles terminating short of the longer baffles at that second end,whereby cooling fluid is able to flow to the second end of the casingbetween alternate pairs of baffles, and then pass around the end of eachshorter baffles of each pair for return flow to the first end of thecasing between next adjacent pairs of baffles; wherein an annularfluid-tight seal is formed between the casing and shell at the secondend; wherein the seal is provided adjacent to the periphery of an endwall of the first sub-housing at the second end, and an electricalenclosure from which electrical power to the motor is received isprovided beyond the second end; and wherein an annular drainage chamberis defined around the perimeter of the end wall such that any coolingfluid passing the seal is received in the chamber and wherein thedrainage chamber has at least one drainage port by which cooling fluidreceived in the drainage chamber is able to pass to the exterior of thepump.
 19. A fluid pump of the type in which a housing assembly has afirst sub-housing having an electric motor therein which is in line witha second sub-housing having an impeller therein, with the motor having arotor shaft which extends through a seal of the first sub-housing intothe second sub-housing and with the impeller mounted on the rotor shaftso as to be rotatable by the motor, and the second sub-housing havinginlet and outlet ports through which fluid, such as water, is able to bepumped through the second sub-housing; wherein the first sub-housingcontaining the motor is of double-walled construction enabling fluidcooling of the motor, with the double-walled construction provided by amotor casing which houses a stator and the rotor shaft of the motor andby an outer shell spaced from and enclosing the motor casing; wherein,within a chamber of the first sub-housing defined between the casing andshell, there is provided a plurality of elongate baffles for guidingcooling fluid for flow over a major part of the external surface of thecasing whereby the operating temperature of the motor is able to becontrolled by heat energy extracted by the fluid from the casing;wherein the baffles are of a form providing for a flow of cooling fluidalong substantially the full axial length of the motor casing; whereinthe baffles provide flow from a first end of the first sub-housingadjacent to the second sub-housing, along the casing to its second endand then back along the casing to the first end by there beingalternating longer and shorter baffles, with the longer bafflesextending substantially to the second end of the casing and the shorterbaffles terminating short of the longer baffles at that second end,whereby cooling fluid is able to flow to the second end of the casingbetween alternate pairs of baffles, and then pass around the end of eachshorter baffles of each pair for return flow to the first end of thecasing between next adjacent pairs of baffles; and further including aheating device in the first sub-housing by which cooling fluidcirculated therethrough is able to be heated to a required degreewhereby, in addition to taking up heat energy from the motor, the fluidcan be further heated such as to maintain fluid circulated by the pumpat a required temperature level; and wherein the heater device ismounted in the motor casing.
 20. The pump of claim 19, wherein theheater device comprises a substrate of a suitable steel with thesubstrate having ceramic overlay on which a heating element and controlcircuitry is provided, such as by printing.
 21. The pump of claim 20,wherein the overlay, with the heating element and circuitry, is formeddirectly onto the motor casing.
 22. The pump of claim 19, wherein theheater device includes a resistance heating element extendingcircumferentially with the motor casing.
 23. The pump of claim 22,wherein the heating element is mounted adjacent to a junction between aperipheral wall of the motor casing and an end wall of the motor casingadjacent to the second sub-housing.
 24. The pump of claim 23, whereinthe motor casing defines an annular channel, around the junction, inwhich the heating element is mounted.
 25. A fluid pump of the type inwhich a housing assembly has a first sub-housing having an electricmotor therein which is in line with a second sub-housing having animpeller therein, with the motor having a rotor shaft which extendsthrough a seal of the first sub-housing into the second sub-housing andwith the impeller mounted on the rotor shaft so as to be rotatable bythe motor, and the second sub-housing having inlet and outlet portsthrough which fluid, such as water, is able to be pumped through thesecond sub-housing: wherein the first sub-housing containing the motoris of double-walled construction enabling fluid cooling of the motor,with the double-walled construction provided by a motor casing whichhouses a stator and the rotor shaft of the motor and by an outer shellspaced from and enclosing the motor casing; and wherein, within achamber of the first sub-housing defined between the casing and shell,there is provided a plurality of elongate baffles for guiding coolingfluid for flow over a major part of the external surface of the casingwhereby the operating temperature of the motor is able to be controlledby heat energy extracted by the fluid from the casing; and wherein thefirst sub-housing has a transverse vent which is located at the end ofthe first sub-housing adjacent to the second sub-housing and which opensto at least one of opposed sides of the first sub-housing and is locatedbetween a respective end wall of the outer-shell of the firstsub-housing and of the motor casing; and wherein the vent is defined bythe end wall of the outer shell, a transverse pair of opposed side wallmembers and a transverse basal wall member which extends between theside wall members, and the shaft extends from the motor casing betweenthe side walls and through the basal and end walls.
 26. The pump ofclaim 25, wherein the end wall of the outer shell comprises a partitionwall which separates the sub-housings, and a seal is provided on theshaft to at least minimise leakage of fluid along the shaft from thesecond sub-housing.
 27. The pump of claim 26, wherein the seal is housedin an annular spigot projecting axially from the outer shell end walltowards or within the first sub-housing.
 28. The pump of claim 25wherein, with the shaft extending horizontally and the vent disposedvertically and opening below the pump, the vent enables fluid whichleaks from the second sub-housing or from the chamber of the firstsub-housing to drain under gravity away from the shaft, therebyminimizing the risk of fluid passing along the shaft to the motorhousing.
 29. The pump of claim 28, wherein the lower end of the vent isplumbed to waste.
 30. The pump of claim 25, wherein the vent is open ateach of its ends and enables air-circulation around the portion of theshaft extending across the vent.
 31. The pump of claim 25, wherein theside walls and the basal wall of the vent are formed integrally with theend wall of the outer shell of the first sub-housing, the basal walldefines a central opening to enable the shaft to extend therethrough andaround that opening, at its face remote from the end wall of the outershell, the basal wall defines an annular spigot with which acorresponding spigot on the end wall of the motor casing co-axiallyoverlaps, a seal is provided between the overlapping spigots, and abearing for the shaft is housed within the overlapping spigots.
 32. Afluid pump of the type in which a housing assembly has a firstsub-housing having an electric motor therein which is in line with asecond sub-housing having an impeller therein, with the motor having arotor shaft which extends through a seal of the first sub-housing intothe second sub-housing and with the impeller mounted on the rotor shaftso as to be rotatable by the motor, and the second sub-housing havinginlet and outlet ports through which fluid, such as water, is able to bepumped through the second sub-housing: wherein the first sub-housingcontaining the motor is of double-walled construction enabling fluidcooling of the motor, with the double-walled construction provided by amotor casing which houses a stator and the rotor shaft of the motor andby an outer shell spaced from and enclosing the motor casing; wherein,within a chamber of the first sub-housing defined between the casing andshell, there is provided a plurality of elongate baffles for guidingcooling fluid for flow over a major part of the external surface of thecasing whereby the operating temperature of the motor is able to becontrolled by heat energy extracted by the fluid from the casing;wherein the flow of cooling fluid is enabled by a plurality of inlet anda plurality of outlet ports for the chamber which provide communicationbetween the interior of the impeller sub-housing and the chamber, withthe inlet ports provided at a higher pressure region of the impellersub-housing and the outlet ports provided at a lower pressure region ofthat sub-housing, whereby a pressure differential prevailing in theimpeller sub-housing provides a force necessary to drive the coolingfluid into and along the chamber from the first to the second end of themotor sub-housing, and then back to the first end for return to theimpeller sub-housing; wherein the inlet ports are disposed radiallyoutwardly with respect to the outlet ports, wherein the number, size andradial location of the inlet and outlet ports enabling the flow ofcooling fluid are chosen to attain a sufficient pressure differentialbetween the inlet and outlet ports to achieve a flow of cooling fluidproviding a suitable level of heat energy extraction from the motorcasing for maintaining the motor at an efficient operating temperatureand to ensure flow through each port which avoids undue generation ofnoise and vibrations; and wherein the first sub-housing has atransversely extending drainage vent which is located at the end of thefirst sub-housing adjacent to the second sub-housing, the vent extendsfrom the shaft and opens to at least one of opposed sides of the firstsub-housing and is located between a respective end wall of theouter-shell of the first sub-housing and of the motor casing, and thetransverse extent of the vent is defined by the end wall of the outershell, a transverse pair of opposed side wall members and a transversebasal wall member which extends between the side wall members, and theshaft extends from the motor casing between the side wall members andthrough the basal wall member and the end wall.
 33. The pump of claim32, wherein the impeller is configured so as to co-operate with asurface of the second sub-housing to assist in maintaining a pressuredifferential between higher and lower pressure regions in the secondsub-housing.
 34. The pump of claim 33, wherein the impeller has anannular spigot or fin which axially overlaps with, is closely adjacentto and co-operates with an annular spigot or fin of the secondsub-housing.
 35. The pump of claim 33, wherein at least one of theimpeller and second sub-housing has a stepped surface which defines anannular face which axially overlaps, is closely adjacent to andco-operates with an annular face, spigot or fin of the other to assistin maintaining the pressure differential.